Process for manufacturing surface-treated wire for use in composite elements of elastomeric material

ABSTRACT

A wire, generally made of steel and used to make composite elements of elastomeric material, is submitted to an electrodeposition process in an electrolytic bath for being coated with a zinc/cobalt alloy in which the average cobalt content is lower than 1%. In the coating thickness made of the zinc/cobalt alloy, different cobalt concentrations exist, that is a 1% to 3% concentration at the area close to the metal wire and a concentration as low as 0.5% maximum at the overlying area. Adhesion promoters for example consisting of cobalt neodecanate, added to the elastomeric material, promote the adhesion of said elastomeric material to the wire.

This is a division of application Ser. No. 08/393,473, filed Feb. 24,1995, now U.S. Pat. No. 5,722,039.

BACKGROUND OF THE INVENTION

The present invention relates to a wire, generally a steel wire,provided with a surface coating of a metal alloy. The invention alsorelates to a process put into practice for carrying out surface-treatingof the wire in question and a composite element obtained byincorporating wires made in accordance with the present invention intoan elastomeric matrix.

It is known that in the manufacture of rubber articles, such as tiresfor motor-vehicles and the like, composite structural elements arewidely used, that is elements made up of a matrix of an elastomericmaterial into which a plurality of wires or metallic cords eachconsisting of a plurality of said wires are incorporated, the functionof which is to give the structural element the necessary features interms of structural strength and geometrical stability.

The wires used for this purpose, generally steel wires, are obtained asa result of a drawing operation carried out at several different timesuntil the desired size is reached, and usually have a coating of a metalalloy on their surface, the essential functions of said coatingconsisting in promoting the drawing capability of the wire and theadhesion of the elastomeric matrix to the coated wire.

To this end, different modalities for making the wire coating have beenproposed.

For example, European Patent EP 296,036 deals with a wire coating madeof copper, brass, tin, zinc or alloys thereof also containing nickel orcobalt for the purpose of improving adhesion of the elastomeric materialto the wire.

In European Patent EP 283,738, filed in the name of the same Applicant,a wire coating is disclosed which consists of two superposed layers madeof a nickel/zinc alloy wherein, in the inner layer, the zinc content isbetween 60% and 90% and in the outer layer the nickel content is in therange of 60% to 80%. In the same patent the possibility of replacingnickel with cobalt in the nickel/zinc alloy is suggested.

In French patents FR 2,413,228 and FR 2,426,562 a wire coated with aternary alloy consisting of brass and cobalt is described, in which thecobalt content is between 0.5% and 30%.

In U.S. Pat. No. 2,296,838 the wire coating consists of an inner layerand an outer layer, made of zinc and cobalt respectively.

U.S. Pat. No. 4,218,517 illustrates the application to a wire of acoating made of a copper/cobalt alloy in which the copper content is inthe range of 10% to 70%.

Finally, U.S. Pat. No. 4,872,932 pertains to a method of makingcomposite elements of an elastomeric material essentially consisting ofa support and a matrix of an elastomeric material fastened thereto. Inthis manufacturing method a film of a thickness included between 10 Åand 100 μm, made of a zinc/cobalt alloy with a cobalt content higherthan 80% is provided to be deposited on said support.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has been found that if thecoating is carried out by electrodeposition of a zinc/cobalt alloyhaving a cobalt content not higher than 1%, optimal features in terms ofdrawing capability and corrosion strength of the wire can besimultaneously achieved, as well as an excellent adhesion of the matrixof elastomeric material to the wires, the attachment values being higheven after aging of the composite element.

In particular, the invention relates to a surface treated wire, adaptedto make composite elements of elastomeric material, characterized inthat said surface coating consists of a zinc/cobalt alloy having acobalt content lower than 1%.

Preferably said coating is obtained by electrodeposition of the coatinglayer on the wire surface, and the cobalt content in the coating layeris lower than 0.5%.

In the coating layer of the drawn wire which has a thickness between 0.1μm and 0.6 μm two different concentration levels of the cobalt materialcan be distinguished and more particularly a level between 1% and 3% atthe radially inner area, that is that directly in contact with the barewire and a level lower than 0.5% in the radially outer area. Thethickness of the radially inner area having a cobalt concentrationgradient between 1% and 3%, is preferably in the range of 0.1 nm to 0.4nm.

Advantageously, said steel wire has a carbon content between 0.6% and0.9% and a diameter after drawing in the range of 0.10 mm to 0.50 mm.

Also an object of the present invention is a process for making asurface treated wire, especially adapted for use with composite elementsof elastomeric material, characterized in that it comprises an immersionstep of the wire into an electrolytic bath containing cobalt sulfate andzinc sulfate, in order to carry out the deposition of a zinc/cobaltalloy on the wire itself, said alloy exhibiting a cobalt content lowerthan 1%.

Preferably, the electrolytic bath is made up of an aqueous solutioncontaining zinc sulfate heptahydrate in an amount between 600 and 630g/l, cobalt sulfate heptahydrate in an amount between 100 and 110 g/l,as well as sodium sulfate in an amount between 70 and 90 g/l.

In a preferred embodiment the electrolytic bath, maintained to atemperature in the range of 25° to 35° C., is passed through by the wirebeing worked at a rate of 15 to 25 meter/minute and the residence timeof the wire in the electrolytic bath has a duration of 5 to 15 seconds.

In an alternative embodiment the electrolytic bath, maintained at atemperature in the range of 50° to 60° C. is passed through by the wirebeing worked at a rate of 40 to 60 meters/minute and the residence timeof the wire in the electrolytic bath has a duration of 2 to 6 seconds.

The electrolytic bath preferably has a pH between 1.5 and 2.5, at 55°C., the value of said pH being adjusted by addition of sulphuric acid.

Referring to a preferred embodiment, a cathodic current of a densitybetween 30 and 40 amperes per square decimeter (A/dm²) is applied to thewire being worked, whereas in the cited alternative embodiment acathodic current of a density between 65 and 85 A/dm² is applied to saidwire.

The process further comprises at least one drawing step carried out onthe wire provided with the coating layer made up of a zinc/cobalt metalalloy, the wire diameter being of a value between 1.2 mm and 1.6 mmbefore drawing and of a value between 0.10 mm and 0.50 mm after drawing.

After drawing the thickness of the coating layer is in the range of 0.1μm to 0.6 μm.

A further object of the present invention is a composite elementcomprising a matrix of an elastomeric material and reinforcing steelwires or cords provided with a metal alloy coating, characterized inthat the wire coating consists of a zinc/cobalt alloy wherein the cobaltcontent is lower than 1%, adhesion promoters being added to theelastomeric material forming said matrix in order to promote adhesion ofsame to said reinforcing wires.

Advantageously said adhesion promoters comprise cobalt neodecanate.

Further features and advantages will become more apparent from thefollowing detailed description, given for illustration purposes only, ofa preferred embodiment of a surface-treated wire to produce compositeelements of elastomeric material and the process for manufacturing saidwire, in accordance with the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

In the following description reference will be made to the enclosedtable reproducing the results of comparison tests carried out on wiresand cords made in accordance with the present invention and on otherwires and relevant cords made according to the known art.

The wire of the present invention is made of steel, preferably of thehigh tensile type, having a carbon content in the range of 0.6% to 0.9%,and it is provided with a surface coating of a metal alloy having a dualfunction: that of preventing corrosion of the wire and that of promotingadhesion to a matrix of elastomeric material into which the wire will beincorporated, in order to form a composite-material structural elementto be used for example in making structural components for tires and thelike.

Since the surface-treated wire is to be submitted to drawing operations,it is also indispensable for the coating to give the wire optimalfeatures in terms of drawing capability.

In accordance with the present invention, in a novel manner it inprovided that the above surface coating should consist of a zinc/cobaltalloy with a cobalt content not higher than 1% and preferably not higherthan 0.5%.

Still in accordance with the invention, said coating is formed by anelectrodeposition process in which said alloy is deposited on the wiresurface. More particularly, in the process for the manufacture of saidsurface-coated wire, the wire continuously fed from a reel, issubmitted, upon an optional pickling step in sulphuric acid, to anelectrolytic bath containing cobalt sulphate and zinc sulphate, in orderto achieve the zinc/cobalt alloy deposition on the wire surface.

Preferably, such an electrolytic bath is made up of an aqueous solutioncontaining zinc sulphate heptahydrate to an amount between 600 and 630g/l, cobalt sulphate heptahydrate to an amount between 100 and 110 g/l,as well as sodium sulphate to an amount between 70 and 80 g/l.Preferably, the pH of the electrolytic bath at a temperature of 55° C.has a value between 1.5 and 2.5. More particularly, the electrolyticbath acidity is preferably adjusted by means of a concentration of H₂SO₄, so as to maintain the predetermined pH value at the predeterminedtemperature.

The temperature of the electrolytic bath, density of the cathodiccurrent applied to the wire being worked and longitudinal feeding rateof the wire (and consequently the residence time of the wire in theelectrolytic bath) have values the adjustments of which depend on eachother, for the purpose of accomplishing the zinc/cobalt alloy depositionaccording to the desired modalities.

In accordance with a preferred embodiment, the electrolytic bath ismaintained at a temperature between 25° C. and 35° C. and the metal wirebeing worked runs through the electrolytic bath at a rate in the rangeof 15 to 25 m/min, the residence time of the wire in the bath beingbetween 5 and 15 seconds.

In such a preferred embodiment, the density of the cathodic currentapplied to the wire is between 30 and 40 Å/dm².

The main parameters relating to the accomplishment of theelectrodeposition process according to a preferred exemplary embodimentof the invention, given just as an indication, are reproducedhereinafter:

overall volume of the electrolytic bath: 290 l ##EQU1## temperature ofthe electrolytic bath=30° C. density of the cathodic current=34 Å/dm²

feed rate of the wire=18 m/min

residence time of the wire in the electrolytic bath=10 seconds.

In accordance with an alternative embodiment, the electrolytic bath ismaintained to a temperature in the range of 50° C. to 60° C., and thewire being worked runs through the electrolytic bath at a rate of 40 to60 m/min, the residence time of the wire in the electrolytic bath beingbetween 2 and 6 seconds.

In the alternative embodiment, the density value of the cathodic currentapplied to the wire is between 65 and 85 Å/dm².

Still by way of example, the fundamental parameters of such a possiblealternative version of the process of the invention are also reproducedhereinafter:

overall volume of the bath: 290 l ##EQU2## temperature of theelectrolytic bath=55° C. density of the cathodic current=75 Å/dm²

feed rate of the wire=50 m/min

residence time of the wire in the electrolytic bath=5 seconds.

In accordance with the present invention, it has been found that theelectrodeposition process carried out according to the above descriptiongives rise to a cobalt concentration at the areas closer to the barewire surface. In the thickness of the coating layer formed as a resultof the electrodeposition on the wire not yet drawn, which in a preferredembodiment has a value in the range of 1 μm to 6 μm, two cobaltconcentration gradients are defined: in the radially innermost area, incontact with the bare wire, having a thickness between 0.1 nm and 0.4nm, the cobalt content is in the range of 1% to 3, whereas in theoverlying area, the radially outermost one, the cobalt content is in theorder of 0.4% and at all events lower than 0.5%.

Still in accordance with the present process, the wire first having adiameter between 1.2 mm and 1.6 mm is submitted after formation of thecoating layer, to a drawing step following which the coated wirediameter is brought to a value between 0.10 mm and 0.50 mm. In addition,as a result of drawing, the thickness of the coating layer is broughtfrom the starting value between 1 μm and 6 μm, to a final value between0.1 μm and 0.6 μm.

After the foregoing it will be apparent that the wire made in accordancewith the present invention exhibits excellent qualities in terms ofdrawing capability, by virtue of the low cobalt concentration present inthe coating layer, and in particular at the peripheral areas of saidlayer which are mostly concerned with the phenomena of surface frictionand wear due to the passage of same through the drawing machines. Inthis connection it is to be pointed out that, as can be seen in thephase diagram of zinc/cobalt binary alloys (Hansen and Anderko 1958),for cobalt contents lower than 1%, and preferably lower than 0.5%, agood drawing capability of the wire can be achieved because the coatinglayer alloy only has the η phase which is stable for cobalt contents upto 0.5%. On the contrary, cobalt contents higher than 1% will give riseto the Υ phase exhibiting a high hardness and therefore low-qualityfeatures in terms of drawing capability.

Therefore, the wire obtained in accordance with the present invention isfree from all the problems usually found in wires coated, according tothe known art, with a double nickel/cobalt or cobalt/zinc layer and,more generally, in wires coated with zinc/cobalt alloys in which thecobalt content is greater than 1%.

In addition, the wire of the invention exhibits surprising qualities ofcorrosion resistant strength, in spite of the low cobalt content presentin the coating layer.

It will be noted in fact that the greater cobalt concentration at thearea immediately close to the bare wire surface obtained by the specificelectrodeposition process gives rise to a greatly higher corrosionresistant strength than usually expected, taking into account the lowcobalt content present on an average in the metal alloy constituting thecoating layer as a whole.

In conclusion, a remarkable corrosion resistant strength in achieved,comparable to that of the wires coated with metal alloys having a cobaltcontent well above 1%, thus eliminating all drawbacks present in wirescoated with brass or copper alloys which have a low corrosion resistantstrength due to the degradation of the steel/coating layer interfaceproduced by galvanic currents.

In addition, the wire of the present invention surprisingly promotesgood rubber/metal attachment quality to the ends of making compositematerials by insertion of wires or reinforcing metal cords made inaccordance with the invention in an elastomeric matrix.

It will be recognized that, in accordance with another feature of theinvention, the rubber/metal attachment quality can be considerablyimproved if appropriate trivalent or pentavalent adhesion promoters areadded to the elastomeric matrix, such as the cobalt neodecanate.

Thus all problems typically found when wires coated with brass or copperalloys are used, are eliminated, which alloys give rise to a great decayof the rubber/metal attachment value due to the copper ion migration inthe elastomeric matrix.

The table below emphasizes the drawing capability, rubber/metal adhesionand corrosion resistant strength features exhibited by the wires andcords of the invention as compared with those of other wires and cordsmade in accordance with the known art, taking the features of aconventional brass-coated wire as the touchstone.

For a better comprehension, it is pointed out that in said table thefeatures found with reference to the brass-coated wires and cords havebeen allocated a value of 100.

First of all, with reference to the drawing capability features, theannexed table highlights that well-known wires coated with a zinc/cobaltalloy in which the cobalt content is in the order of 4% and those coatedwith a double Zn/Co or Zn/Ni layer respectively have a coating losspercentage (column A) four times and twice that of the brass-coatedwires, by "loss percentage" meaning the percent amount of material byweight which is taken away from the coating layer as a result ofdrawing. In the wire made according to the present invention, the losspercentage substantially corresponds to that of the brass-coated wires.

Still with reference to the drawing capability, it will be noted thatthe number of wire breakages by amount of drawn wire (column B)occurring on the zinc-cobalt coated wires having a cobalt content of 4%and the zinc/cobalt or zinc/nickel double layered wires was respectivelyin the order of three times and twice that occurred in brass-coatedwires, the drawing conditions being equal.

On the contrary, the wire made in accordance with the present inventionexhibits about the same number of breakages as the brass-coated wire.

As regards the adhesion quality, it is pointed out that it has beentested by evaluating the force necessary for extracting a cord length ofthe 1×4×0.25 type (four wires with a diameter of 0.25 mm twistedtogether) from a sample blend in which said cord is incorporated (a testdone according to ASTM D-2229 standard).

Such a test has been carried out both on samples directly coming fromthe vulcanization step of the composite material (column C) and onsamples previously submitted to an aging process (Column D), consistingin keeping the samples 8 days in a climatic chamber having a humiditycontent of 90%, and a temperature of 65° C., according to the abovementioned ASTM standard.

The test enables the qualitative degradation to adhesion resulting fromnatural aging of the tires in use to be evaluated.

Due to the very bad drawing capability of the wires having a cobaltcontent equal to 4%, it has been impossible to make wires thin enough toenable their use for producing cords designed to carry out comparativetests relating to adhesion resistance and corrosion resistant strengthwithin the composite element.

As can be seen, the cord formed of wires coated with a doublezinc/cobalt or zinc/nickel layer shows, immediately after vulcanization,a lower attachment level than a cord formed of brass-coated wires.However the attachment level offered by this type of known wires keepsalmost constant over time, so that, after aging, it has the same valueas that offered by cords formed of brass-coated wires, as said cordsundergo a qualitative decay as a result of said aging. The wiresmanufactured according to the present invention exhibit attachmentlevels similar to those of the cords having brass-coated wires, bothafter the vulcanization step and after said aging.

As regards the corrosion resistant strength (Column E), as measured byevaluating the rust amount present on a treated wire in a saltyenvironment according to ASTM-B117/73 standard, it is possible to findthat both wires made according to the invention and wires coated with azinc/cobalt or zinc/nickel double layer show a strength 50 times higherthan that of the brass-coated wires.

The corrosion strength has been also evaluated on a series of fourmotor-vehicle tires, size 180/60R14, by machine tests and not by roadtests, measuring the corrosion spreading in time.

More particularly, each tire provided with a belt comprising a pair ofstrips of rubberized fabric reinforced with said cords type 1×4×0.25,has been rotated on a roller test bench at a speed of 80 km/h for aperiod of time of 100 hours (Column F) and 200 hours (Column G).

At the equatorial plane of the tire six holes with a diameter of 1 mmhave been produced, said holes extending from the radially inner surfaceof the tread to the area between the two belt strips; then a salinesolution containing 125 g of salt (NaCl) in half a liter of water hasbeen introduced into the tire.

At the end of the test the tread has been taken away from the tire andthe qualitative evaluation of the rubberizing state of the belt cordshas been carried out.

The presence of bare cords, that is devoid of rubber, has been ascribedto the rubber/metal bond decay due to the migration of the salinesolution along the cord.

In the table below one can see that the corrosion resistant strength inthe cords having wires according to the invention is 30 times higherthan that of the cords having brass-coated wires after a 100 hour test,and becomes 50 times higher after a 200 hour test, thanks to a lowerpropagation velocity of the corrosion.

Obviously, many modifications and variations may be made to theinvention as conceived, all of them falling within the scope of theclaims hereinafter.

                                      TABLE                                       __________________________________________________________________________                     Rubber/Metal                                                   Wire drawing Attachment Corrosion strength                                    capability Level on a wire in a tire                                        Wire Coating                                                                          A    B   C    D   E     F   G                                         __________________________________________________________________________    Brass   100  100 100  100  100   100                                                                               100                                        Zn/Co .sub.--  4% 400 300 = = = = =                                           Zn/Co--Zn/Ni 200 200  80 100 5000 = =                                         Zn/Co < 1% 100 100 100 100 5000 3000 5000                                   __________________________________________________________________________

I claim:
 1. A process for making a surface-treated steel wire, adaptedfor use in composite elements of elastomeric material, comprising thesteps of:immersing the wire in an electrolytic bath containing cobaltsulfate and zinc sulfate, for carrying out a deposition of a zinc/cobaltalloy on the outer surface of the treated wire, said alloy having acobalt content effective to promote adhesion, said alloy having anoverall cobalt content lower than 1% and said alloy having an absence ofcopper, wherein said deposition is an electrodeposition in which acathodic current is applied to the wire during said immersing step toprovide said wire with an outermost surface coating layer, in which insaid surface coating layer the cobalt is distributed in an uneven mannerin two different concentration levels, with a first level between 1% and3% at a radially inner area directly in contact with the steel wire anda second level lower than 0.5% in a radially outer area overlying thefirst level.
 2. A process according to claim 1 in which the thickness ofthe radially inner area having a cobalt concentration gradient between1% and 3%, is in the range of 0.1 nm to 0.4 nm.
 3. A process accordingto claim 1, wherein said electrolytic bath consists essentially ofcobalt sulfate, zinc sulfate and sodium sulfate.
 4. A process for makinga surface-treated steel wire, adapted for use in composite elements ofelastomeric material, comprising the steps of:immersing the wire in anelectrolytic bath containing cobalt sulfate and zinc sulfate, forcarrying out a deposition of a zinc/cobalt binary alloy on the outersurface of the treated wire, said binary alloy having a cobalt contenteffective to promote adhesion, said binary alloy having an overallcobalt content lower than 1%, and said binary alloy having an absence ofcopper, wherein said deposition is an electrodeposition in which acathodic current is applied to the wire during said immersing step toprovide said wire with a surface coating layer.
 5. A process accordingto claim 4 in which the electrolytic bath is made up of an aqueoussolution containing zinc sulfate heptahydrate in an amount between 600and 630 g/l, cobalt sulfate heptahydrate in an amount between 100 and110 g/l, as well as sodium sulfate in an amount between 70 and 80 g/l.6. A process according to claim 5 including maintaining the electrolyticbath at a temperature in the range of 25° to 35° C. and passing the wiretherethrough at a rate of 15 to 25 meters/minute, the residence time ofthe wire in the electrolytic bath having a duration of 5 to 15 seconds.7. A process according to claim 6 including applying a cathodic currentof a density between 30 and 40 A/dm² to the wire being worked.
 8. Aprocess according to claim 5 including maintaining the electrolytic bathat a temperature in the range of 50° to 60° C. and passing the wiretherethrough at a rate of 40 to 60 meters/minute, the residence time ofthe wire in the electrolytic bath having a duration of 2 to 6 seconds.9. A process according to claim 8 including applying a cathodic currentof a density between 65 and 85 A/dm² to the wire being worked.
 10. Aprocess according to claim 5 including maintaining the electrolytic bathat a pH between 1.5 and 2.5, at 55° C., the value of said pH beingadjusted by addition of sulphuric acid.
 11. A process according to claim4 in which the thickness of the coating layer present on the wire afterthe immersion step in the electrolytic bath is between 1 μm and 6 μm.12. A process according to claim 4 including carrying out at least onedrawing step on the wire provided with the coating layer made up of azinc/cobalt alloy.
 13. A process according to claim 12 in which the wirediameter before drawing has a value between 1.2 mm and 1.6 mm and, afterdrawing, a value between 0.10 and 0.50 mm.
 14. A process according toclaim 13 in which after drawing, the thickness of the coating layer isbetween 0.1 μm and 0.6 μm.
 15. A process according to claim 4, whereinthe cobalt content in the coating layer is lower than 0.5%.
 16. Aprocess according to claim 4, wherein the cobalt concentration of thealloy increases at regions of the coating closer to the bare wiresurface.
 17. A process according to claim 4 wherein, the content ofcobalt in a radially inner area of said coating directly in contact withthe metal wire being between 1% and 3%, and the content of cobalt in aradially outer area overlaying said radially inner area being aneffective amount to affect the adhesion of said elastomeric material butlower than 0.5%.
 18. A process according to claim 4, whereintheelectrolytic bath is made up of an aqueous solution containing zincsulfate heptahydrate in an amount between 600 and 630 g/l, cobaltsulfate heptahydrate in an amount between 100 and 110 g/l, as well assodium sulfate in an amount between 70 and 80 g/l; the electrolytic bathis maintained at a temperature in the range of 25° to 35° C. and passingthe wire therethrough at a rate of 15 to 25 meters/minute, the residencetime of the wire in the electrolytic bath having a duration of 5 to 15seconds; the pH of the electrolytic bath is maintained at between 1.5and 2.5 at 55° C., the value of the pH being adjusted by addition ofsulphuric acid; and a cathodic current density between 30 and 40 A/dm²is applied to the wire being worked.
 19. A process according to claim 4,whereinthe electrolytic bath is made up of an aqueous solutioncontaining zinc sulfate heptahydrate in an amount between 600 and 630g/l, cobalt sulfate heptahydrate in an amount between 100 and 110 g/l,as well as sodium sulfate in an amount between 70 and 80 g/l; theelectrolytic bath is maintained at a temperature in the range of 50° to60° C. and passing the wire therethrough at a rate of 40 to 60meters/minute, the residence time of the wire in the electrolytic bathhaving a duration of 2 to 6 seconds; the pH of the electrolytic bath ismaintained at between 1.5 and 2.5 at 55° C., the value of the pH beingadjusted by addition of sulphuric acid; and a cathodic current densitybetween 65 and 85 A/dm² is applied to the wire being worked.
 20. Aprocess according to claim 4 in which the steel wire has a carboncontent between 0.6% and 0.9%.
 21. A process according to claim 4,further comprising drawing the coated wire wherein the outermost coatingof said drawn wire is said surface coating layer.
 22. A processaccording to claim 21, further comprising reinforcing an elastomericmaterial with a member of the group consisting of said drawn wire andcords of said drawn wire.
 23. A process for making a surface-treatedsteel wire, adapted for use in a composite element of elastomericmaterial, comprising the steps of:i) immersing the wire in anelectrolytic bath containing cobalt sulfate and zinc sulfate, forcarrying out a deposition of a zinc/cobalt alloy on the outer surface ofthe treated wire, said alloy having a cobalt content effective topromote adhesion, said alloy having an overall cobalt content lower than1%, and said alloy having an absence of copper,wherein said depositionis an electrodeposition in which a cathodic current is applied to thewire during said immersing step to provide a surface coating layer ofsaid alloy on the wire, ii) drawing said surface-coated wire; and iii)reinforcing the elastomeric material with a member of the groupconsisting of said drawn surface-coated wire and cords of said drawnsurface-coated wire, wherein said surface coating consists of saidzinc/cobalt alloy, and wherein the composite element contains adhesionpromoters.
 24. A process according to claim 23, wherein said adhesionpromoters comprise cobalt neodecanate.
 25. A process according to claim23, in which in said surface coating layer the cobalt is distributed inan uneven manner in two different concentration levels, with a firstlevel between 1% and 3% at a radially inner area directly in contactwith the steel wire and a second level lower than 0.5% in a radiallyouter area overlying the first level.
 26. A process according to claim23, wherein said surface coating layer has a thickness between 0.1 μmand 0.6 μm.